The present invention relates to golf balls and, more particularly, to improved golf balls having low spin rates. The improvement in the golf balls results from a unique dual, or multilayer core which is relatively soft and a hard cover made from blends of one or more specific hard, high stiffness ionomers. The combination of a soft dual or multilayer core and a hard cover leads to an improved golf ball having a lower than anticipated spin rate while maintaining the resilience and durability characteristics necessary for repetitive play. In an additional embodiment of the invention, the spin rate is further reduced by decreasing the weight of the softened dual or multilayer core while maintaining core size and by increasing the thickness or weight of the cover. The larger, less dense finished dual core or multilayer ball exhibits lower spin rates after club impact than conventional balls.
Spin rate is an important golf ball characteristic for both the skilled and unskilled golfer. High spin rates allow for the more skilled golfer, such as PGA professionals and low handicap players, to maximize control of the golf ball. This is particularly beneficial to the more skilled golfer when hitting an approach shot to a green. The ability to intentionally produce xe2x80x9cback spin,xe2x80x9d thereby stopping the ball quickly on the green, and/or xe2x80x9cside spinxe2x80x9d to draw or fade the ball, substantially improves the golfer""s control over the ball. Thus, the more skilled golfer generally prefers a golf ball exhibiting high spin rate properties.
However, a high spin golf ball is not desirous by all golfers, particularly high handicap players who cannot intentionally control the spin of the ball. In this regard, less skilled golfers, have, among others, two substantial obstacles to improving their game: slicing and hooking. When a club head meets a ball, an unintentional side spin is often imparted which sends the ball off its intended course. The side spin reduces one""s control over the ball as well as the distance the ball will travel. As a result, unwanted strokes are added to the game.
Consequently, while the more skilled golfer desires a high spin golf ball, a more efficient ball for the less skilled player is a golf ball that exhibits low spin properties. The low spin ball reduces slicing and hooking and enhances roll distance for the amateur golfer.
The present inventors have addressed the need for developing a golf ball having a reduced spin rate after club impact, while at the same time maintaining the durability, playability and resiliency characteristics needed for repetitive use. The reduced spin rate golf ball of the present invention meets the rules and regulations established by the United States Golf Association (xe2x80x9cU.S.G.A.xe2x80x9d).
Along these lines, the U.S.G.A. has set forth five (5) specific regulations to which a golf ball must conform. The U.S.G.A. rules require that a ball be no smaller than 1.680 inches in diameter. However, notwithstanding this restriction, there is no specific limitation as to the maximum permissible diameter of a golf ball. As a result, a golf ball can be as large as desired so long as it is larger than 1.680 inches in diameter and so long as the other four (4) specific regulations are met.
The U.S.G.A. rules also require that balls weigh no more than 1.620 ounces, and that their initial velocity may not exceed 250 feet per second with a maximum tolerance of 2%, or up to 255 ft./sec. Further, the U.S.G.A. rules state that a ball may not travel a distance greater than 280 yards with a test tolerance of 6% when hit by the U.S.G.A. outdoor driving machine under specific conditions.
It has been determined by the present inventors that the combination of a relatively soft dual or multilayer core (i.e. an overall core Riehle compression of about 75 to 160) and a hard cover (i.e. Shore D hardness of 65 or more) significantly reduces the overall spin rate of the resulting golf ball. The inventors have also learned that an increase in cover thickness, thereby increasing the overall diameter of the resulting molded golf ball, further reduces spin rate.
Top-grade golf balls sold in the United States may be generally classified as one of two types: two-piece or three-piece balls. The two-piece ball, exemplified by the balls sold by Spalding and Evenflo Companies, Inc. (the assignee of the present invention through its wholly owned subsidiary, Lisco, Inc.) under the trademark TOP-FLITE, consists of a solid polymeric core and a separately formed outer cover. The so-called three-piece balls, exemplified by the balls sold under the trademark TITLEIST by the Acushnet Company, consist of a liquid (e.g., TITLEIST TOUR 384) or solid (e.g., TITLEIST DT) center, elastomeric thread windings about the center, and a cover.
Spalding""s two-piece golf balls are produced by molding a natural (balata) or synthetic (i.e. thermoplastic resin such as an ionomer resin) polymeric cover composition around a preformed polybutadiene (rubber) core. During the molding process, the desired dimple pattern is molded into the cover material. In order to reduce the number of coating steps involved in the finishing of the golf balls, a color pigment or dye and, in many instances, an optical brightener, are added directly to the generally xe2x80x9coff whitexe2x80x9d colored polymeric cover composition prior to molding. By incorporating the pigment and/or optical brightener in the cover composition molded onto the golf ball core, this process eliminates the need for a supplemental pigmented painting step in order to produce a white or colored (notably orange, pink and yellow) golf ball.
With respect to multi-layered golf balls, Spalding is the leading manufacturer of two-piece golf balls in the world. Spalding manufactures over sixty (60) different types of two-piece balls which vary distinctly in such properties as playability (i.e. spin rate, compression, feel, etc.), travel distance (initial velocity, C.O.R., etc.), durability (impact, cut and weather resistance) and appearance (i.e. whiteness, reflectance, yellowness, etc.) depending upon the ball""s core, cover and coating materials, as well as the ball""s surface configuration (i.e. dimple pattern). Consequently, Spalding""s two-piece golf balls offer both the amateur and professional golfer a variety of performance characteristics to suit an individual""s game.
In regard to the specific components of a golf ball, although the nature of the cover can, in certain instances, make a significant contribution to the overall feel, spin (control), coefficient of restitution (xe2x80x9cC.O.R.xe2x80x9d) and initial velocity of a ball (see, for example, U.S. Pat. No. 3,819,768 to Molitor), the initial velocity of two-piece and three-piece balls is determined mainly by the coefficient of restitution of the core. The coefficient of restitution of the core of wound (i.e. three-piece) balls can be controlled within limits by regulating the winding tension and the thread and center composition. With respect to two-piece balls, the coefficient of restitution of the core is a function of the properties of the elastomer composition from which it is made.
The cover component of a golf ball is particularly influential in affecting the compression (feel), spin rates (control), distance (C.O.R.), and durability (i.e. impact and may be adjusted to optimize the desired properties of the resulting golf balls.
Over the last twenty (20) years, improvements in cover and core material formulations and changes in dimple patterns have more or less continually improved golf ball distance. Top-grade golf balls, however, must meet several other important design criteria. To successfully compete in today""s golf ball market, a golf ball should be resistant to cutting and must be finished well; it should hold a line in putting and should have good click and feel. In addition, the ball should exhibit spin and control properties dictated by the skill and experience of the end user.
With respect to the increased size of the ball, over the years golf ball manufacturers have generally produced golf balls at or around the minimum size and maximum weight specifications set forth by the U.S.G.A. There have, however, been exceptions, particularly in connection with the manufacture of golf balls for teaching aids. For example, oversized, overweight (and thus unauthorized) golf balls have been on sale for use as golf teaching aids (see U.S. Pat. No. 3,201,384 to Barber).
Oversized golf balls are also disclosed in New Zealand Patent No. 192,618 dated Jan. 1, 1980, issued to a predecessor of the present assignee. This patent teaches an oversize golf ball having a diameter between 1.700 and 1.730 inches and an oversized core of resilient material (i.e. about 1.585 to 1.595 inches in diameter) so as to increase the coefficient of restitution. Additionally, the patent discloses that the ball should include a cover having a thickness less than the cover thickness of conventional balls (i.e. a cover thickness of about 0.050 inches as opposed to 0.090 inches for conventional two-piece balls).
In addition, it is also noted that golf balls made by Spalding in 1915 were of a diameter ranging from 1.630 inches to 1.710 inches. As the diameter of the ball increased, the weight of the ball also increased. These balls were comprised of covers made up of balatalgutta percha and cores made from solid rubber or liquid sacs and wound with elastic thread.
Golf balls known as the LYNX JUMBO were also commercially available by Lynx in October, 1979. These balls had a diameter of 1.76 to 1.80 inches. The LYNX JUMBO balls met with little or no commercial success. The balls consisted of a core comprised of wound core and a cover comprised of natural or synthetic balata.
However, notwithstanding the enhanced diameters of these prior golf balls, none of these balls produced the enhanced spin reduction characteristics and overall playability, distance and durability properties of the present invention and/or fell within the regulations set forth by the U.S.G.A. An object of the present invention is to produce a U.S.G.A. regulation golf ball having improved low spin properties while maintaining the resilience and durability characteristics necessary for repetitive play.
As noted, a number of two-piece (a solid resilient center or core with a molded cover) and three-piece (a liquid or solid center, elastomeric winding about the center, and a molded cover) golf balls have been produced. The different types of materials utilized to formulate the cores, covers, etc. of these balls dramatically alters the balls"" overall characteristics. In addition, multi-layered covers containing one or more ionomer resins and other combinations of thermoplastic materials have also been formulated in an attempt to produce a golf ball having the overall distance, playability and durability characteristics desired.
Despite the great number of materials and combinations of materials utilized in prior art golf balls, there still remains a need for an improved golf ball exhibiting superior properties.
These and other objects and features of the invention will be apparent from the following summary and description of the invention and from the claims.
The present invention is directed to improved golf balls having a low rate of spin upon club impact. The golf balls comprise a dual, or multilayer core component that is preferably soft, and further comprise a relatively hard cover. The hard cover may preferably be sized to produce a ball that is larger than conventional diameters. The low spin rate enables the ball to travel a greater distance. In addition, the low spin rate provides the less skilled golfer with more control. This is because the low spin rate decreases undesirable side spin which leads to slicing and hooking. The combination of a hard cover and a soft core provides for a ball having a lower than anticipated spin rate while maintaining high resilience and good durability.
Through the use of the softer cores and the hard cover, overall finished balls of the invention exhibit significantly lower spin rates than conventional balls of equal size and weight. Further, reduction in spin is also produced by increasing the thickness of the cover and by decreasing the weight of the softened core.
In a first aspect of the present invention, a low spin golf ball is provided, comprising a dual or multilayer core having a center component and a core layer disposed about the center component. The dual core is relatively soft, having an overall core Riehle compression of at least about 75. The golf ball further comprises a relatively hard cover disposed about the dual core. The cover has a Shore D hardness of at least about 65.
In another aspect, the present invention provides a low spin golf ball comprising a dual core having a center component and a core layer disposed about the center component. The golf ball further comprises a multi-layer cover disposed about the dual core. The cover is relatively hard, having a Shore D hardness of at least about 65.
In another aspect, the present invention provides a low spin golf ball comprising a dual core having a center component that includes a thermoplastic material and a core layer that includes a thermoset material. The core has a Riehle compression of at least about 75. The golf ball further comprises a cover disposed around the dual core, the cover having a Shore D hardness of at least about 65.
In yet another aspect, the present invention provides a golf ball comprising a dual core having a center component that includes a thermoset material and a core layer comprising a thermoplastic material. The core has a Riehle compression of at least about 75. The golf ball further comprises a cover disposed about the dual core configuration. The cover is relatively hard, having a Shore D hardness of at least about 65.
In a further aspect, the present invention provides a low spin golf ball comprising a dual core having a center component and a core layer disposed about the center component. The center component and the core layer both comprise a thermoplastic material. The core has a Riehle compression of at least about 75. The low spin golf ball further comprises a cover surrounding the dual core. The cover has a Shore D hardness of at least about 65.
In yet another aspect, the present invention provides a low spin golf ball comprising a dual core having a center component and a core layer disposed about the center component. The golf ball further comprises a cover disposed on the dual core, the cover comprising a particular high acid ionomer resin, and/or a certain alpha olefin.
In all aspects, the covers may be in the form of a multilayer cover described in greater detail herein.
Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. It should, however, be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art.